Here is a great quote that falls into the category of “you are what you eat”.
“What you pay attention to in the world is what you’re going to end up knowing”, from Happiness: Unlocking the Mysteries of Psycological Wealth, by Robert Biswas-Diener.
It’s okay to be under the influence of someone or a group. Let yourself be open to change and associate with people of like minded thinking and interests. It will be very good for you.